fix(brain): move the wikilink strip into WriteNote/UpdateNote

The BrainStore is not the only door. POST /write — the HTTP path CLAUDE.md
hands to curl and scripts — calls api.WriteNote directly, so the strip
shipped one commit ago covered brain_write and capture while leaving the raw
door ungated. A gate one door wide is not a gate.

The BrainStore keeps its own call so it can still report Ref.Unlinked to the
MCP caller; running the strip twice is a no-op on content the primitive has
already cleaned.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ingestion/internal/api/update.go

@@ -64,6 +64,14 @@ func UpdateNote(brainDir string, opts UpdateNoteOptions) (relPath, contentHash,
 		return "", "", "", fmt.Errorf("content is required")
 	}
 
+	// Same reason as WriteNote: the strip belongs in the primitive so every
+	// door inherits it.
+	clean, _, err := brain.StripUnresolvedLinks(brainDir, opts.Content)
+	if err != nil {
+		return "", "", "", err
+	}
+	opts.Content = clean
+
 	var rel string
 	if opts.Path != "" {
 		rel = opts.Path